1. Field of the Invention
This invention relates to a lens barrel, and more particularly, to a lens barrel having a flare diaphragm member disposed therein for cutting off harmful incident light.
2. Related Art Statement
In the past, various proposals have been made to provide a lens barrel having a flare diaphragm member provided therein for cutting off harmful incident light.
One such example of a lens barrel is shown in Japanese Utility Model Application Laid-Open No. (Sho)63-160520. More specifically, this application describes an inner surface reflection-proof device for a zoom lens having at least two groups or front and rear groups of movable lenses moved in a direction of an optical axis thereof so as to provide zooming. In the zoom lens, there is provided a reflection-proof member such as a flare stop or diaphragm for blocking harmful light rays which would otherwise reach the surface of loaded film. The reflection-proof member is positioned behind the rear lens group so as to be movable in the direction of the optical axis. The reflection-proof member is moved to a predetermined position in response to movement of the rear lens group. Further, when a cam ring to be driven into rotation on the optical axis is pivoted, then the groups of movable lenses and the reflection-proof member are consequently moved together in the direction of the optical axis.
Another example is shown in Japanese Utility Model Application Laid-Open No. (Hei)2-5714. More specifically, this application contains a zoom lens barrel in which a cam ring is supported on a stationary cylinder so as to be movable in a direction of an optical axis thereof in response to rotation. Further, the cam ring has a lens-guiding ring provided thereon. The lens-guiding ring has a lens-guiding ring provided thereon. The lens-guiding ring is moved jointly with the cam ring in the direction of the optical axis, while being relatively rotated with respect to the cam ring in response to movement of the cam ring in the direction of the optical axis. The lens-guiding ring and the cam ring are respectively provided with cam grooves and lens-guiding grooves, which grooves are adapted for use with at least two groups or front and rear groups of movable lenses. These lenses are provided with guide pins which are inserted between the cam grooves and lens-guiding grooves. The cam groove and the lens-guiding groove are configured in shape to move the front and rear groups of movable lenses on a predetermined trajectory by way of a motion combined between the optical axis-along-movement and relative rotation of the cam ring and lens-guiding ring. In addition, a light-sealing plate such as a flare diaphragm for shutting off harmful light rays is provided at a rear end of the lens-guiding ring.
However, the device according to the above-described Application No. (Sho)63-160520 requires a space inside the lens barrel to extend the cam ring or to be connected to the cam ring. Such a requirement contributes to a larger-sized lens barrel.
In the zoom lens barrel according to the preceding Application No. (Hei)2-5714, a position of the light-sealing plate such as the flare diaphragm is defined by the lens-guiding ring. As a result, there are cases where the light-sealing plate such as the flare diaphragm cannot be disposed at a position which is the most effective in cutting off incident harmful light.